1) Field of the Invention
The present invention relates to a method for washing textile and the like, especially in large scale industrial applications, and to a system for carrying out this method.
2) Prior Art
Water is one of the most important elements in a washing process whereby the object is to clean articles, for example textile, subjected to said process. As well as water, the washing result is dependent on other factors such as wash temperature, detergent and the mechanical action of washing.
There is a growing need for improved wash processes, especially with a particular emphasis on reducing the amount of water used due to the scarcity thereof in particular areas, and during hot seasons. Methods are also currently sought for reducing the amount of detergent used in order to prevent environmental problems which result when the detergent is released into the environment after use.
In certain areas of England for example, water is rationed during hot summers leading to problems for laundromats and industrial laundries.
Furthermore in some remote areas with poor access, such as the Greek islands, water has to be transported there by truck. This means that when this water is finished, there is a shortage of water until the next delivery. This is especially a problem for hotel laundries on such islands.
Moreover the price of water is ever increasing so that ways to reduce water usage are becoming increasingly sought after.
Due to these problems, much research has been done into the recycling of water in washing processes.
An existing method for treating water in a washing machine is described in the European patent application 0 467 028 from Zanussi.
This application describes a method for filtering water by means of reverse osmosis for domestic washing machines and dish washers, which has the object of softening the water, so that the amount of detergent necessary to provide an effective wash can be reduced. Purified water from the reverse osmosis step is stored in a tank until needed in the washing machine.
The concentrate from the reverse osmosis filter (which contains contaminants) is guided away, and kept in a separate tank such that this concentrate can be used for carrying out the first rinse cycle on a subsequent wash program.
Water from the last rinse from the previous wash program is returned to the first tank from where water is guided to the reverse osmosis unit whereby about 20% of the water in any giving wash program is recycled.
An object of the present invention is to provide an improved washing process wherein water is recycled for reuse in both main wash and rinse cycles while retaining and reusing heat in water.
According to a first aspect the present invention provides a process for washing objects such as textile and the like, comprising the steps of:
a) guiding water and detergent into a washing machine;
b) carrying out one or more wash and/or rinse cycles In the machine;
c) guiding the water from step b) into a reverse osmosis unit, where the water is subjected to reverse osmosis in order to remove contaminants from the water;
d) recycling water front step c) into the washing machine for use by one or more wash and/or rinse cycles wherein substantially all the recycled water is subjected to the reverse osmosis step c).
A significant saving in water and energy is provided with this process, with a reverse osmosis unit, contamination with a molecular weight of  less than 100 can be separated.
The recycled water is preferably used in at least two separate rinse cycles, and most preferably in a subsequent washing program.
Rinsing consumes a large part of the water necessary in washing processes especially with white wash for example for hotel and hospital linen. Until now, waste water from washing machines has not been resused for rinsing this sort of textile washed in the machine due to the risk of textile damage. In general, fresh mains water is used for this.
The water quality requirements for rinsing are different than for the use of water by other wash program phases. One of the main differences in the quality requirements of rinse water is the salt content thereof. If this salt content is too high in the so-called finishing equipment, it is difficult to treat the textile, whereby brown stains are caused on the textile which can also yield skin irritations. Waste water from the washing process has a high salt content mainly due to the salts present in the detergent. On using the process according to the present invention purified water can however be recycled for reuse in the rinsing phases where the main part of water is required for an individual program.
It is preferable to subject water which enters the washing cycle for the first time to a pre-treatment step (for example pre-filtration), before it enters the washing machine.